The present invention relates to a sheet feeding sheet feeding device for a printer or the like. More specifically, the present invention relates to control of a sheet supply roller provided in the sheet feeding device.
Generally, a printer such as an inkjet printer employs a sheet feeding device, which holds a plurality of sheet in a stacked manner, and feeds the sheets into the printer one by one along a sheet feed path thereof. Such a sheet feeding device generally includes a sheet supply roller, which is typically driven by a stepping motor.
When held by the sheet feeding device, the plurality of stacked sheets are inclined with respect to the vertical direction, and the leading end of the plurality of sheets are abutted against a sheet separating plate, which generally has a surface formed of minute volley and ridge portions extending perpendicular to the sheet feeding direction so as to have relatively high friction coefficient. The sheet supply roller is arranged to contact the top one of the stacked sheet. As the sheet supply roller rotates, the leading end of the top sheet is moved against the frictional force, and fed along the sheet feed path.
Such a configuration may cause a problem as follows.
If the leading end of the top sheet is engaged with the volley portion formed on the sheet separating plate, and the sheet supply roller is rotated to separate the top sheet, the leading end may not move at an initial stage and then may be suddenly released from the volley portion. In such a case, the leading end of the top sheet may move excessively in the feeding direction. In addition, since the sheet supply roller is generally biased to the stack of sheets and configured to be movable in a direction away from the sheets, sheet feeding due to the above-described movement of the top sheet, the sheet supply roller may be lifted by an impact force of the top sheet.
In addition, the sheet supply roller may be deteriorated with age, and in such a case, the sheets may not be fed properly. In another case, if the leading end of the sheet is curved, the sheet may not be properly fed.
The present invention is advantageous in that it provides a sheet feeding device and a method with which a top sheet is stably separated from a stack of sheets.
According to an embodiment, there is provided a sheet feeding device which feeds a stack of sheets one by one along a sheet feed path. The sheet feeding device includes a sheet driving member that separates and drives one sheet of the stack of sheets in the sheet feed direction, and a control system that controls the sheet driving member to move the one sheet at least in a first mode that is followed by a second mode. The control system controls the sheet driving member to move the one sheet at a first speed in the first mode, and at a second speed in the second mode. The first speed is smaller than the second speed.
With this configuration, it is ensured that the top sheet of the stacked sheets is properly separated when the second mode starts.
Optionally, predetermined stop time is provided between the first mode and the second mode, and the sheet driving member stops moving the one sheet during the predetermined stop time.
Further optionally, the predetermined stop time may be varied in accordance with a thickness of the sheet to be fed.
Still optionally, at least one of the first and second speed may be changed in accordance with a thickness of the sheet to be fed.
According to embodiments, the sheet feeding device further includes a separating plate located on downstream side, with respect to a sheet feed direction, of the stack of sheets. Leading ends of the stack of sheets are abut against a surface of the separating plate. The surface of the separating plate is formed to be a rough surface. The one sheet to be fed is a top sheet of the stack of sheets, and the sheet driving member contacts the top sheet of the stack of sheets. The sheet driving member is driven to move the top sheet in the sheet feed direction.
According to embodiments, the sheet feeding device is configured to feed the leading end of the top sheet from a first position which is on the sheet separating plate to a predetermined registration position, the leading end being detached from the sheet separating plate at located at a second position at an end of drive in the first mode, the leading end being moved from the second position to the predetermined registration position during the second mode.
In this case, the sheet feeding device is further provided with a registration sensor that detects absence/presence of a sheet, the registration sensor being provided at a third position which is located between the second position and the predetermined registration position.
Optionally, the control system judges an occurrence of a sheet feed error based on the operation mode and a status detected by the registration sensor.
If the registration sensor detects presence of a sheet at the end of operation in the first mode, the control system judges an occurrence of a sheet feed error. In this case, a notification of the occurrence of the error may be issued. In particular, in the above case, since the sheet is already located at the registration sensor, it is preferable that the sheet is fed and discharged.
In an alternative case, if the registration sensor does not detect presence of a sheet by the end of operation in the second mode, the control system judges an occurrence of a sheet feed error.
According to another aspect of the invention, there is provided a sheet feeding device which feeds a stack of sheets one by one along a sheet feed path. The sheet feeding device further includes a sheet driving member that separates and drives one sheet of the stack of sheets in the sheet feed direction, and a control system that controls the sheet driving member to move the one sheet from a stacked position to a predetermined registration position, the control system being selectively operates in a first feeding mode and a second feeding mode. In this case, the control system controls the driving member to move the one sheet in a first mode that is followed by a second mode when the first feeding mode is selected, the control system controls, in the first feeding mode, the sheet driving member to move the one sheet at a first speed in the first mode, and the sheet driving member to move the one sheet at a second speed in the second mode. In this case, the first speed is slower than the second speed.
Optionally, the control system controls the driving member substantially at a constant speed in the second feeding mode.
Further optionally, the control system may control the driving member to move the one sheet in a third mode that is followed by a fourth mode when the second feeding mode is selected, and the control system controls, in the second feeding mode, the sheet driving member to move the one sheet at a third speed in the third mode, and the sheet driving member to move the one sheet at a fourth speed in the fourth mode.
In a particular case, the third speed is slower than the second speed.
Still optionally, at least one of the constant speed, first speed and second speed may be changed depending on a thickness of a sheet to be fed.
Further optionally, a predetermined stop time is provided between the first mode and the second mode, and the sheet driving member stops moving the one sheet during the predetermined stop time.
In this case, the predetermined stop time may be varied in accordance with a thickness of the sheet to be fed.
The sheet feeding device may further include a sheet feed error detection system, and a storage that accumulatively stores the number of occurrences of the sheet feed error.
In this case, the control system may select one of the first feeding mode and the second feeding mode in accordance with the accumulated number of occurrences of the sheet feed error.
Optionally, the control system may select the first feeding mode if the number of occurrences of subsequent sheet feed errors reaches a predetermined value.
According to embodiments, there is provided a method of feed a stack of sheets one by one from the stack to a predetermined registration position along a sheet feed path of a sheet feeding device. The method includes driving one sheet of the stack of sheets in the sheet feed direction to a position upstream side of the predetermined registration position at a first speed, and driving one sheet in the sheet feed direction to the predetermined registration position at a second speed which is different from the first speed.
With this method, it is ensured that the top sheet of the stack of sheets is properly separated and fed. The method can be stored in a storage medium as a program which can be executed by a computer system.
Optionally, the first speed is slower than the second speed.
According to embodiments, there is provided a method of feed a stack of sheets one by one from the stack to a predetermined registration position along a sheet feed path of a sheet feeding device, which includes driving one sheet of the stack of sheets in the sheet feed direction to a position upstream side of the predetermined registration position at a first speed, stopping the one sheet to move for a predetermined period of time, and driving the one sheet in the sheet feed direction to the predetermined registration position at a second speed which is different from the first speed.
With this method, it is also ensured that the top sheet of the stack of sheets is properly separated and fed to the registration position. The method can be stored in a storage medium as a program which can be executed by a computer system.